The present invention relates to devices and methods for dispensing, delivering or administering substances, including, in one embodiment, a device and a method for dosing or dispensing a preferably injectable substance in doses or selected amounts from an injection or infusion device. More particularly, the present invention relates to a device and a method for setting and/or measuring a dispensed dosage of a substance or a dosage of the substance to be dispensed.
EP 0 581 925 B1 and corresponding U.S. Pat. No. 5,509,905, the disclosures and teachings of which are incorporated herein by reference, disclose an injection apparatus comprising an operating button using which switching means can be operated which engage with a switch piece wherein they operate switches, wherein the number of partial rotations of the operating button is indicated on a indicating means and an axial movement of the operating button can only be performed at the end of such a partial rotation. While this ensures that the operating button is operated in a defined way, errors may occur when setting a dosage.
In general, setting a dosage to be dispensed needs to be performed exactly. It is also preferable that the setting be monitored, and any errors occurring during the setting procedure should be recognized.
In order to code four rotational positions, coding the four positions using a Gray code is for example known, as shown in FIG. 4, such that in the two-digit binary code shown, the coding of neighbouring positions differs only by changing a single bit. If, for example, an error occurs in the second bit, such that it remains constantly set to zero, the transition from Position A to Position B is not recognized by the value “00” which then remains unchanged, and the subsequent transition from Position B to Position C with the erroneous code “10” is erroneously interpreted as a transition from Position A to Position B (coding: 00 to coding: 10), such that the rotational direction is incorrectly interpreted.
If four rotational positions A to D with four intermediate states resulting from changes in state are coded using three bits, as shown in FIG. 5, then the rotational direction can for example be incorrectly interpreted if the first bit erroneously remains at the value 0. A transition from the intermediate state bc (coding: 001) to Position C (correct coding: 101; erroneous coding: 001) is not recognized. A subsequent transition to the intermediate state cd (correct coding: 111; erroneous coding: 011) is interpreted as a transition from the intermediate state bc to Position B.
Thus, through a single erroneous bit, the exemplary codings shown in FIGS. 4 and 5 can result in a rotational direction opposite to the actual rotational direction being determined. Thus, for example, an increase in a set dosage may be erroneously interpreted as a reduction in the dosage amount and, for example, a warning erroneously may not be output or signalled when a dosage is set too high.